Plassmeyer was optioned the Phillies' spring training complex Sunday.
The 26-year-old was called up to start the penultimate contest of the regular season Saturday in Game 2 of the doubleheader against the Mets, but he was rocked for 10 runs (nine earned) across 3.2 innings. Plassmeyer spent most of the campaign at Triple-A Lehigh Valley and posted a 5.05 ERA in 14 starts, so he's unlikely to receive a look during the playoffs for Philadelphia.